1. Field of the Invention
The present invention is generally in the field of semiconductor fabrication. More specifically, the invention is in the field of fabrication of capacitors in semiconductor dies.
2. Background Art
High performance mixed signal and RF circuits require high density integrated capacitors. Metal-insulator-metal (“MIM”) capacitors can be considered for use in the fabrication of integrated mixed signal and RF circuits on semiconductor dies. Disadvantageously, typical MIM capacitors have low capacitance density and since RF and mixed signal applications require high capacitance values, the die area consumed by typical MIM capacitors is too large and results in increased die costs to the manufacturer and the user.
Moreover, semiconductor dies that include typical MIM capacitors pose significant problems for interconnect routing because the metal plates used in the MIM capacitors prevent effective utilization of interconnect metal layers for their primary purpose, i.e. for interconnect routing. For example, use of several MIM capacitors or one large MIM capacitor would significantly hinder interconnect routing in a die. The reason is that large MIM capacitor plates would result in smaller available area for interconnect lines and would also require longer interconnect lines taking a “detour” around the large obstacles created by MIM capacitor plates present in the same interconnect metal layer where interconnect routing is to take place. Thus, lack of interconnect design flexibility and undesirably long interconnect lines, as well as consumption of significant die area by MIM capacitor plates are significant drawbacks in the use of MIM capacitors in mixed signal and RF applications.
Therefore, a need exists for mixed signal and RF MIM capacitors that are dense and that further do not adversely affect interconnect routing.